RE: icalendar.el bug fix patch

[Drew Adams <drew.adams@oracle.com>]

>> But since the concept is useful, how about if we
>> create an escape for it? For example, we could
>> establish \! as a regexp that matches any single
>> character.
> 
> +1.

[Interesting.  I skipped this thread, based on the
Subject.  Just stumbled on this part of it, about
having a simple pattern to match what `\\(.\\|[\n]\\)'
matches.  Wouldn't have guessed that from the Subject.]

FWIW, I proposed this back in 2006.  Actually, I
proposed a toggle, so you could use the _same_ regexp
to match either any char or any char except newline.

Nothing wrong with having a separate escape, such as
`\!', to always match what `\\(.\\|[\n]\\)' matches.

But it would still be good to (also) have a toggle,
to be able to make just `.' match the same thing.

https://lists.gnu.org/archive/html/emacs-devel/2006-03/msg00162.html

In 2012 I again voiced the proposal (in the context
of mentioning how Icicles lets you do such things):

  I proposed long ago, for instance, a toggle for a
  `.' in regexp search to match also newlines, i.e.,
  any character.  IOW, `.' in one mode state of the
  toggle, would be equivalent to "\\(.\\|[\n]\\)"
  in the other (traditional) state.

https://lists.gnu.org/archive/html/emacs-devel/2012-08/msg00832.html

So how about adding an escape, such as `\!', and
_also_ adding a toggle (variable and command to
toggle it) that treats both `\!' and plain `.' the
same; that is; have them each match any char?